CN110061692B - Shutdown system for series photovoltaic module and restarting method thereof - Google Patents

Shutdown system for series photovoltaic module and restarting method thereof Download PDF

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CN110061692B
CN110061692B CN201810053115.5A CN201810053115A CN110061692B CN 110061692 B CN110061692 B CN 110061692B CN 201810053115 A CN201810053115 A CN 201810053115A CN 110061692 B CN110061692 B CN 110061692B
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shutdown
turn
main switch
terminal
series
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CN110061692A (en
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张永
顾在学
胡晓磊
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Fonrich Shanghai New Energy Technology Co ltd
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Fonrich Shanghai New Energy Technology Co ltd
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    • H02J3/383—
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
    • H02S40/30—Electrical components
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/567—Circuits characterised by the use of more than one type of semiconductor device, e.g. BIMOS, composite devices such as IGBT
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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Abstract

The invention mainly relates to a shutdown system for a series photovoltaic module and a restarting method thereof. The shutdown system comprises at least one shutdown control module and one or more shutdown devices, a plurality of photovoltaic assemblies are connected in series to form a battery string and are also connected in series with the shutdown devices, and the shutdown devices are used for performing shutdown operation on the battery string connected in series with the shutdown devices; when receiving a shutdown command, the shutdown control module stops transmitting a periodic excitation pulse source to the shutdown device to inform the normally-off shutdown device to perform shutdown operation on the battery string connected with the normally-off shutdown device in series; or the shutdown control module starts to transmit a periodic excitation pulse source to the shutdown device to inform the normally-on shutdown device to perform shutdown operation on the battery string connected with the normally-on shutdown device in series when receiving the shutdown command. The simple shutdown topology is used for achieving a high-reliability shutdown scheme, and a scheme of restarting the serially-connected multi-stage photovoltaic modules again after being switched by a shutdown system is further provided.

Description

Shutdown system for series photovoltaic module and restarting method thereof
Technical Field
The invention mainly relates to the technical field of photovoltaic power generation, in particular to a shutdown system capable of rapidly shutting down a series of multi-stage photovoltaic modules, a high-reliability shutdown scheme is achieved by using a simple shutdown topological structure, and a scheme for restarting the series of multi-stage photovoltaic modules again after being switched by the shutdown system is also provided.
Background
Photovoltaic power generation systems considered to be in the high voltage field need to meet electrical safety regulations. In recent years, in countries such as the united states and europe, mandatory requirements are gradually added to relevant electrical specifications for safety. Corresponding laws and regulations are respectively set for governments or related organizations of various countries. Based on electrical mandated codes, the american fire protection association modifies national electrical regulations requiring, in residential photovoltaic power generation systems: when an emergency occurs, the voltage of the direct current end is limited not to exceed eighty volts to the maximum extent after the alternating current grid-connected port of the photovoltaic power generation system is disconnected. Italian safety regulations caution: firefighters are absolutely not allowed to perform a fire extinguishing operation with a building charged with voltage. Germany also has first implemented fire safety standards and also stipulates in plain text: an additional direct current cut-off device needs to be added between an inverter and a component in the photovoltaic power generation system.
Taking the safety code NEC2017 in the united states as an example, the photovoltaic power generation system is required to have a rapid turn-off function, and the voltage between the conductors inside the photovoltaic array and between the conductors and the ground must not exceed about eighty volts at most after turn-off. The photovoltaic power station should actively take the following measures in the face of safety regulations: in order to realize rapid shutdown, a shutdown device for shutdown must be installed at the output end of the photovoltaic module, and a command sending device is installed on a battery string for supplying direct current or a direct current bus, and the command sending device needs to be controlled manually. For example, in case of fire, it is necessary to turn off the photovoltaic module quickly, and the command transmitting device is used to instruct the turn-off device to turn off. The countermeasure of shutting down the photovoltaic module can prevent further deterioration of negative events such as fire and the like, and improve reliability and safety.
Disclosure of Invention
In an embodiment of the invention, a shutdown system for tandem photovoltaic modules is disclosed comprising: at least one shutdown control module and one or more shutdown devices; a plurality of photovoltaic modules are connected in series to form a battery string and are also connected in series with a turn-off device; the shutdown device is used for performing shutdown operation on the battery string connected with the shutdown device in series; when receiving a turn-off command, the turn-off control module stops transmitting an excitation pulse source to the turn-off device to control the normally-off type turn-off device to perform turn-off operation on the battery pack string connected in series with the normally-off type turn-off device; or the shutdown control module starts to transmit an excitation pulse source to the shutdown device when receiving the shutdown command so as to control the normally-on shutdown device to perform shutdown operation on the battery string connected with the normally-on shutdown device in series.
The shutdown system for the tandem photovoltaic module described above, wherein: the turn-off device comprises a main switch and a first coupling transformer, wherein the main switch and the first coupling transformer are connected with the photovoltaic module in series through a power line; a primary winding of the first coupling transformer is connected in series with a main switch provided with a first terminal, a second terminal and a control terminal; the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on a power line; the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode, and the potential of the energy storage capacitor is used for controlling the main switch to be switched off or switched on.
The shutdown system for the tandem photovoltaic module described above, wherein: in a normally-off turn-off device, when the potential of the energy storage capacitor reaches the turn-on threshold voltage of the main switch, the main switch is turned on, otherwise, the main switch is turned off; in the normally-on type turn-off device, when the potential of the energy storage capacitor reaches the turn-off threshold voltage of the main switch, the main switch is turned off, otherwise, the main switch is turned on.
The shutdown system for the tandem photovoltaic module described above, wherein: in a Normally-OFF (Normally OFF) shut-OFF device: the main switch is an enhanced Metal Oxide Semiconductor Field Effect Transistor (MOSFET), so that the first terminal, the second terminal and the control terminal are respectively a source electrode, a drain electrode and a grid electrode, and the main switch is an Insulated Gate Bipolar Transistor (IGBT), so that the first terminal, the second terminal and the control terminal are respectively an emitter electrode, a collector electrode and a grid electrode of the main switch; in a turn-off device of the normal type (Normally ON): the main switch is a depletion mode JFET or a depletion mode power MOSFET and the first, second and control terminals are a source, a drain and a gate, respectively. The above-mentioned shutdown system: a parallel resistor connected in parallel with the energy storage capacitor is arranged between the control terminal and the first terminal of the main switch. The above shutdown system for a tandem photovoltaic module: a voltage stabilizing diode connected with the energy storage capacitor in parallel is arranged between the control terminal and the first terminal of the main switch; or a pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are arranged between the control terminal and the first terminal of the main switch.
The shutdown system for the tandem photovoltaic module described above, wherein: the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch; the dotted terminal of the secondary winding of the first coupling transformer is coupled to the control terminal of the main switch through the steering diode; the dotted terminal is connected to the anode of the steering diode and the control terminal of the main switch is connected to the cathode of the steering diode. The above shutdown system for a tandem photovoltaic module: the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch; the dotted terminal of the secondary winding of the first coupling transformer is coupled to a first node through a first capacitor; a first diode is connected between the synonym end of the secondary winding of the first coupling transformer and a first node; the anode of the first diode is connected to the synonym terminal of the secondary winding of the first coupling transformer, and the cathode is connected to the first node; the first node is coupled to the anode of the steering diode and the control terminal of the main switch is coupled to the cathode of the steering diode.
The shutdown system for the tandem photovoltaic module is described above, wherein the shutdown device is further configured to perform an operation of recovering the string of the battery string connected in series to the shutdown system from the shutdown state to the re-series connection state; in the normally-off type turn-off device: when receiving a starting command, the shutdown control module transmits an excitation pulse source to the shutdown device through the power line again to inform the shutdown device to execute the operation of re-series connection on the battery pack string connected with the shutdown device in series; or in a normally-on type shut-off device: the shutdown control module, upon receiving a start command, stops delivering the excitation pulse source to the shutdown device through the power line to inform the shutdown device to perform the re-series connection operation on the string of battery cells connected in series therewith.
The shutdown system for the tandem photovoltaic module described above, wherein: in the normally-off or normally-on type turn-off device, the turn-off device includes a parallel capacitance connected between a first terminal and a second terminal of the main switch; the turn-off device thus performs a turn-off operation and, after the main switch is closed, a conduction path for the excitation pulse source to propagate on the power line is provided by a parallel capacitance connected in parallel with the main switch. The shutdown system for the tandem photovoltaic module described above, wherein the shutdown control module further includes a second coupling transformer and first and second switches: setting a first switch and a primary winding of a second coupling transformer to be connected in series between a direct current power supply and a reference ground, and setting a second switch to be connected in parallel with the primary winding; the driving signal drives the first switch to switch between on and off, and the second switch is complementary with the first switch, so that the primary winding of the second coupling transformer is intermittently excited by the direct-current power supply and generates an excitation pulse source; and the secondary winding of the second coupling transformer is connected with the plurality of photovoltaic modules in series through a power line, and the secondary winding of the second coupling transformer is used for coupling the excitation pulse source to the power line.
The shutdown system for the series photovoltaic module described above, wherein the primary winding of the second coupling transformer is coupled to the dc power supply through the first switch: a first resistor is connected between the primary winding of the second coupling transformer and the reference ground; or a first resistor and a capacitor connected in parallel with the first resistor are connected between the primary winding of the second coupling transformer and the reference ground.
In another non-limiting alternative embodiment of the invention, the method for restarting the shutdown system for the tandem photovoltaic module after shutdown is disclosed as described above: the turn-off device comprises a main switch and a first coupling transformer, wherein the main switch and the first coupling transformer are connected with the photovoltaic module in series through a power line; a primary winding of the first coupling transformer is connected in series with a main switch provided with a first terminal, a second terminal and a control terminal; the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on a power line; the inductive excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode, and the potential of the energy storage capacitor is used for controlling the main switch to be switched off or switched on; the method comprises the following steps: in the normally-off type turn-off device: when the turn-off control module receives a starting command, the turn-off control module transmits an excitation pulse source to the turn-off device again to start charging the energy storage capacitor until the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch and turns on the main switch, and the turn-off device is triggered to execute the operation of recovering from the turn-off state to the re-series connection state on the battery pack string connected with the turn-off device in series; or in a normally-on type shut-off device: when the turn-off control module receives the starting command, the drive pulse source is stopped being transmitted to the turn-off device through the power line to prohibit the energy storage capacitor from being charged, the potential of the energy storage capacitor drops below the turn-off threshold voltage of the main switch and the main switch is switched on, and the turn-off device is triggered to carry out the operation of recovering from the turn-off state to the re-series connection state on the battery pack string connected with the main switch in series. The method comprises the following steps: in the normally-off or normally-on type turn-off device, the turn-off device includes a parallel capacitance connected between a first terminal and a second terminal of the main switch; when the turn-off device performs a turn-off operation and turns off the main switch, a parallel capacitor connected in parallel with the main switch provides a conduction path through which the excitation pulse source propagates on the power line.
Safety level factors of the photovoltaic power generation system must be considered, and the sum of the photovoltaic power generation system items suggested by the U.S. NEC2017-690.12 standard is taken as an example, the photovoltaic power generation system is required to have a component-level turn-off capability to provide the best system safety. Through the foregoing explanation of the present application, if it is attempted to control the voltage to rapidly drop below 30 v, the shutdown control module stops sending the excitation pulse to the shutdown devices to inform the shutdown devices to shut down the respective corresponding photovoltaic modules when receiving an external shutdown command issued by human beings, or starts sending the excitation pulse source to the shutdown devices to control the normally-on shutdown devices to perform shutdown operations on the battery strings connected in series therewith when receiving the external shutdown command. Therefore, the voltage of the direct current bus is approximately equal to zero volt, and the safety is high. It is obvious that the shutdown solution at the component level disclosed in the present application has the capability of automatic shutdown of the component, and typical applications of the present application include: can be used for preventing the irreversible damage of the components and the junction box caused by the heat generation caused by fire, hot spots or overlarge wiring resistance of the junction box.
In the present application, the shutdown command may be not only from an external shutdown command issued manually, but also from an internal shutdown command, for example, when the shutdown control module detects a high temperature or an open fire or the like through a sensor, the shutdown command of the shutdown control module may be generated by being triggered by various target faults. Finding how the system recovers after shutdown is again a new concern after meeting the shutdown capabilities at the component level, and the solution is as follows.
In the present application, when the shutdown control module receives the start command, the power line transmits an excitation pulse, such as a square wave, to the shutdown device to charge the energy storage capacitor, so that the potential of the energy storage capacitor reaches a turn-on threshold voltage of a Normally-OFF main switch (Normally OFF) to turn on the main switch. When the turn-off control module receives the starting command, the excitation pulse source is stopped being transmitted to the turn-off device, the energy storage capacitor is not charged, the potential of the energy storage capacitor falls below the turn-off threshold voltage of the Normally-open main switch (Normally ON), and the main switch is switched ON. The shutdown device can be triggered to perform the operation of recovering from the shutdown state to the re-serial connection state on the battery string connected in series with the shutdown device, and the voltage supply to the bus can be recovered.
Drawings
To make the above objects, features and advantages more comprehensible, embodiments accompanied with figures are described in detail below, and features and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the following figures.
Fig. 1 is a schematic diagram of an architecture in which photovoltaic modules are connected in series to form a battery string and a plurality of battery strings are connected in parallel.
Fig. 2 is an architecture for configuring a shutdown device for a photovoltaic module and a shutdown control module for a battery string.
Fig. 3 is an embodiment of a battery string in which the turn-off control module instructs the turn-off device to turn on or off.
Fig. 4 is a turn-off device in the battery string that performs turn-on or turn-off in cooperation with an instruction of the turn-off control module.
Fig. 5 is a diagram of the shutdown control module sending an excitation pulse signal onto the power line that can be received by the shutdown device.
Fig. 6 is an alternative embodiment of a shutdown control module with a coupling transformer to generate a source of excitation pulses.
Fig. 7 is an embodiment of a shutdown control module improved circuit topology for generating an excitation pulse source.
FIG. 8 is an embodiment in which more of the excitation pulse source power can be absorbed by the storage capacitor per switching cycle.
Fig. 9 is an embodiment of a shutdown device in which a normally-off power switch is replaced with a normally-on power switch.
Detailed Description
The technical solutions of the present invention will be clearly and completely described below with reference to various embodiments, but the described embodiments are only used for describing and illustrating the present invention and not for describing all embodiments, and the solutions obtained by those skilled in the art without making creative efforts belong to the protection scope of the present invention.
In the field of photovoltaic power generation, a photovoltaic module or a photovoltaic cell is a core component of power generation. Solar panels are classified into monocrystalline silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells and the like in the mainstream technology, the required service life of the silicon cells is as long as more than twenty years, and monitoring of the durability of the output characteristics of the cells is essential. Many internal and external factors contribute to inefficient power generation of photovoltaic modules: conversion efficiency is reduced due to manufacturing differences or installation differences between the photovoltaic modules themselves or shading or maximum power tracking adaptation. Taking the shielding as an example, if a part of the photovoltaic modules are shielded by clouds, buildings, tree shadows, dirt and the like, the part of the photovoltaic modules can be changed into a load by a power supply and does not generate electric energy any more, the temperature of the photovoltaic modules at a local position with a serious hot spot effect is higher, and some parts of the photovoltaic modules can exceed several hundred degrees centigrade to cause permanent damage such as burning or dark spots, welding spot melting, packaging material aging, glass explosion, corrosion and the like, so that great potential hazards are caused to the long-term safety and reliability of the photovoltaic modules. The photovoltaic power generation system needs to solve the following problems: it is very important to be able to take active safety shutdown measures for various faults. The U.S. national electrical code states that the voltage of all photovoltaic power generation systems needs to drop below 30 volts within 10 seconds, and a shutdown device serving as a shutdown function must be configured for the output of the photovoltaic module based on the function of achieving rapid shutdown.
Referring to fig. 1, a photovoltaic module array is the basis for the conversion of light energy to electrical energy in a photovoltaic power generation system. The battery string installed in the photovoltaic module array is shown, with respect to the battery string: each battery string is formed by connecting a plurality of photovoltaic modules which are mutually connected in series, and the photovoltaic modules can be replaced by direct current power supplies such as fuel cells or chemical batteries. A plurality of different battery strings are connected in parallel: although each battery string is composed of a plurality of photovoltaic modules and the plurality of photovoltaic modules are connected in series, a plurality of different battery strings are connected in parallel with each other and collectively supply electric energy to an energy collecting device such as an inverter INVT. At a certain electricityIn the string of batteries, the present application takes as an example the series type of multi-stage photovoltaic modules PV1-PVN, their respective output voltages VO1-VONSuperposed to provide the total string voltage with a higher potential to the inverter INVT, i.e. the bus voltage VBUSThe inverter INVT performs inversion from direct current to alternating current after summarizing the output power of each of the serially connected multi-stage photovoltaic modules, and N is a natural number greater than 1. A large-capacity bus capacitor C is connected between the DC buses LA-LB for providing DC power supply for the inverterDCIn the photovoltaic power generation system, the bus capacitor is required to realize decoupling between constant input power and fluctuating output power of the inverter. If the load needs direct current instead of alternating current, the inverter INVT can be replaced by a direct current/direct current converter for supplying power to the load, and the direct current/direct current converter sums the output power of each of the serially connected multi-stage photovoltaic modules and then performs direct current-to-direct current conversion.
Referring to fig. 2, each photovoltaic cell or photovoltaic module in an embodiment is configured with a device for performing monitoring and shutdown, that is, a shutdown device for short. In a certain battery string: the electric energy generated by the first-stage photovoltaic module PV1 is determined by the first-stage shutdown device SD1 to be superimposed on the whole battery string, the electric energy generated by the second-stage photovoltaic module PV2 is determined by the second-stage shutdown device SD2 to be superimposed on the whole battery string, and the electric energy generated by the nth-stage photovoltaic module PVN is determined by the nth-stage shutdown device SDN to be superimposed on the whole battery string. The main function of the shut-off device is explained below, for example: the first-stage shutdown device SD1 to the nth-stage shutdown device SDN need to establish communication with another shutdown control module RSD (Rapid Shut-Down), the communication mechanism is compatible with various current communication schemes such as power line carrier communication or various wireless communications, and the shutdown control module RSD at least needs to be equipped with a human-computer interaction function, that is, can receive commands from human beings. If a fire occurs in a power station for various reasons, a fire fighter must first shut down the entire power generation system to fight the fire, otherwise high voltages may jeopardize personal safety. Taking the artificial active operation turn-off control module RSD as an example: when the shutdown control module RSD receives a shutdown command, for example, an emergency shutdown switch provided therein is pressed to indicate that a shutdown command is reached, at this time, the shutdown control module RSD immediately issues a first command, that is, a shutdown command, to the multiple shutdown devices SD1-SDN based on communication, and may be represented by a logic level signal, so as to notify the multiple shutdown devices SD1-SDN to shut down the respective corresponding photovoltaic modules PV1-PVN, so that the voltage output by the battery string connected between the dc buses LA-LB immediately drops to approximately zero as desired.
Referring to fig. 2, in an optional but not required embodiment, it is assumed that a first stage PV1, a second stage PV2, and so on, are connected in series inside a string of cells to the nth stage PV. It can be learned that the total string-level voltage that can be provided on an individual battery string is approximately equal to: voltage V output by first stage photovoltaic module PV1O1Plus the voltage V output by the photovoltaic module PV2 of the second stageO2Then, the voltage V output by the photovoltaic module PV3 of the third stage needs to be addedO3…, and so on, to the voltage value V of the output of the photovoltaic module PVN of the Nth stageONThe total cascade voltage is calculated to be equal to VO1+VO2+…VON. The cascade voltage obtained by superposing the voltages output by the multi-stage photovoltaic modules on the bus LA-LB is transmitted to electric equipment such as a combiner box or an inverter for combination and inversion, and then grid connection is carried out. The plurality of photovoltaic modules PV1-PVN correspond to the plurality of shut-off devices SD1-SHN, in particular: the first-stage shutdown device SD1, the second-stage shutdown devices SD2, …, and so on up to the nth-stage shutdown device SDN, and so on are connected in series by a power line. The shutdown device is used for shutting down the photovoltaic component corresponding to the shutdown device to remove the photovoltaic component from the battery string or restoring the photovoltaic component corresponding to the shutdown device from the shutdown state to the series connection state of the connection battery string.
Referring to fig. 2, it is mentioned that when the shutdown control module RSD sends a so-called shutdown command to the shutdown devices SD1-SDN, the shutdown devices SD1-SDN are notified to shut down the corresponding photovoltaic modules PV1-PVN to secure the system. The voltage between the dc buses LA-LB can be pulled down as quickly as desired to be nearly equal to zero for safety, while the shutdown control module RSD is ready to receive a start command. The start command may be generated at any time, for example, a fire alarm occurs to cut off the entire battery string, and after the fire alarm is released, the system needs to be restarted to allow the photovoltaic power generation system to enter the working state again to supply voltage to the bus. The field of photovoltaic power generation is directed to so-called turn-off devices for photovoltaic modules, the basic function of which is to turn a photovoltaic module off or on.
Referring to fig. 2, the control mode of the system restart after shutdown consists in: the shutdown control module RSD, upon receiving the start command, sends a start instruction opposite to the aforementioned shutdown instruction to the plurality of shutdown devices SD1-SDN to inform the plurality of shutdown devices to restore the respective corresponding photovoltaic modules PV1-PVN from the shutdown state to the series-connected state. The foregoing informs that the shutdown control module RSD needs to be equipped with at least a human-computer interaction function, and the start command may be a command issued manually. An activation command is then transmitted, for example, by pressing an activation switch provided in the so-called shutdown control module RSD, which immediately issues a second command, i.e., an activation command, which can be represented by a logic level signal, to the shutdown device SD1-SDN on the basis of the communication. The photovoltaic modules PV1-PVN are brought back from the off-state to the series-connected state, and the voltage output by the battery string connected between the dc buses LA-LB as desired immediately supplies the buses with a cascade voltage, which has a very high voltage level and can typically be as high as several hundred volts or even thousands of volts.
Referring to fig. 2, compared to fig. 1 without any shutdown device, the embodiment of fig. 2 has a fast shutdown function and meets the safety specification, but the embodiment of fig. 2 uses too many shutdown devices, and the number of the shutdown devices is equal to the number of photovoltaic modules, which not only causes too high cost but also makes communication between the shutdown control module RSD and the shutdown devices SD1-SDN difficult, so that it is necessary to use fewer shutdown devices to achieve the same purpose.
Referring to fig. 3, it is observed throughout the string of batteries in which the multilevel photovoltaic modules PV1-PVN are connected in series: the negative terminal of any previous-stage photovoltaic assembly is coupled to the positive terminal of the adjacent next-stage photovoltaic assembly, so that the following conditions are met: the maximum total string voltage provided by a certain battery string is equal to the final superposition value of the output voltages of the photovoltaic modules PV1-PVN in the plurality of battery strings. The specific relationship is as follows: the cathode output end O2 of the first-stage photovoltaic module PV1 is coupled to the anode output end O1 of the adjacent succeeding photovoltaic module PV2, the cathode output end O2 of the second-stage photovoltaic module PV2 is coupled to the anode output end O1 of the adjacent succeeding photovoltaic module PV3, and the cathode output end O2 of the photovoltaic module of the Nth-1 stage is coupled to the anode output end O1 of the succeeding photovoltaic module PVN. Therefore, cascade voltage obtained by superposing the voltages output by the photovoltaic modules is transmitted to the energy collecting device. It is also observed that the positive output O1 of the first stage photovoltaic module is coupled to the bus bar LA, and that the negative output O2 of the last nth stage photovoltaic module is coupled to the bus bar LB. The embodiment of fig. 3 differs slightly from fig. 2: each of the multi-stage photovoltaic modules in fig. 2 is assigned one turn-off device, but fig. 3 shares one turn-off device. The separate shut-off device SD shown in fig. 3 is much less expensive than fig. 2, the position of the shut-off device SD being arbitrary: the photovoltaic module can be arranged between the negative output end O2 of the last Nth photovoltaic module and the bus bar LB, can be arranged between the positive output end O1 of the first photovoltaic module PV1 and the bus bar LA, and can be arranged between the negative output end of any previous photovoltaic module and the positive output end of the adjacent next photovoltaic module. The general principle is as follows: the multi-stage photovoltaic modules are connected in series to form a battery string and are also connected in series with the shutdown device SD. The embodiment of fig. 2 has the advantage of more flexibility in being able to control the turn off or turn on of each component individually.
Referring to fig. 3, the series shutdown system as the name implies that the shutdown device SD and the multi-stage photovoltaic module are connected in series, and includes: the shutdown control module RSD and the shutdown device SD, the photovoltaic modules PV1-PVN are connected in series to form a battery string and they are also connected in series with the shutdown device SD, which is used to perform a shutdown operation on the battery string connected in series with it. When the turn-off control module RSD receives the turn-off command, for example, the turn-off command can be expressed by pressing an emergency turn-off switch/turn-off button/touch screen type turn-off switch equipped in the turn-off control module, and the turn-off control module RSD has a human-computer interaction function. The mode in which the shutdown control module RSD issues a so-called shutdown command to the shutdown device SD adopts the following scheme: when the shutdown control module RSD controls the shutdown device SD to be in the normal on state to ensure that the shutdown device SD and the battery string are connected in series, it needs to send the excitation pulse source PUS to the shutdown device SD uninterruptedly or at least intermittently or periodically, and at this time, the battery string including the photovoltaic modules PV1-PVN is directly connected in series between the buses LA-LB because the shutdown device SD is on, so that it can contribute a higher voltage level to the buses; in contrast, if the shutdown control module RSD stops sending the so-called excitation pulse source PUS to the shutdown device SD when the shutdown device SD is in the shutdown state, so that the battery string is removed from between the dc buses LA to LB, the battery string containing the photovoltaic modules PV1 to PVN is itself directly removed from between the buses LA to LB because the shutdown device SD is in the shutdown state, that is, electric energy cannot be further contributed to the buses. The mode in which the shutdown control module instructs shutdown to the shutdown device SD can be roughly considered as: the supply of the periodic excitation pulse source PUS to the shut-down device SD is stopped to inform the shut-down device SD to perform a shut-down operation on the battery string connected in series therewith.
Referring to fig. 3, the shutdown device SD comprises a main switch M and a first coupling transformer T1Main switch M and first coupling transformer T1A plurality of photovoltaic modules PV1-PVN are connected in series between the busbars by power lines. The power line or series line referred to herein may actually be considered as an extension of the bus bar. The main switch M may be a power MOSFET, i.e. a metal oxide semiconductor field effect transistor, or an IGBT, i.e. an insulated gate bipolar transistor, or an equivalent power switch. The main switch is a three-port electronic switch, the metal oxide semiconductor field effect transistor comprises a grid electrode, a source electrode and a drain electrode, and the insulated gate bipolar transistor comprises a grid electrode, a collector electrode and an emitter electrode. The main switch of the MOSFET has a drain electrodeD and has a first terminal such as a source S and a control terminal such as a gate G, and the main switch of the insulated gate bipolar transistor has a second terminal such as a collector C and has a first terminal such as an emitter E and a control terminal such as a gate G. The turn-on characteristic of a general mosfet is turned on when a voltage value up to a turn-on threshold voltage is applied between the gate and the source, and the turn-on characteristic of a general igbt is turned on when a voltage value up to a turn-on threshold voltage is applied between the gate and the emitter. Typical power semiconductor switching devices include metal oxide semiconductor field effect transistors, bipolar transistors, thyristors, gate turn-off thyristors, emitter turn-off thyristors, integrated gate commutated thyristors, insulated gate bipolar transistors, etc. It is apparent that the series of photovoltaic modules is connected in series between the first and second terminals of the main switch.
Referring to fig. 3, a first coupling transformer T1The primary winding L1 is connected in series with a main switch M having a first terminal and a second terminal and a control terminal, the signal at the control terminal of the main switch M determining whether the first terminal and the second terminal of the main switch M are on or off, and the coupling transformer can be replaced by a current transformer. First coupling transformer T1Its secondary winding L2 is then used to extract or inductively switch off the excitation pulse source PUS that the control module RSD loads onto the power line, which may be a pulsating voltage and is most common with square waves, because of the coupling effect. In order to satisfy the condition that the secondary winding L2 can induce and capture the excitation pulse source PUS, a first coupling transformer T1The synonym terminal of the secondary winding L2 is coupled to the first terminal of the main switch M, i.e. to a common node NCO, which is provided with a reference ground potential GR. First coupling transformer T1The dotted terminal of secondary winding L2 is coupled to a control terminal, e.g., gate G, of the main switch M through a steering diode D2. Specifically, the method comprises the following steps: first coupling transformer T1Is coupled to a first node N1 via a first capacitor CC, the steering diode D2 is connected between the first node N1 and a control terminal of the main switch, and the steering diode D2 is connected between the control terminal of the main switch and the second node N1The anode terminal of the diode D2 is connected to the first node N1 and the cathode terminal is connected to the control terminal of the main switch. At the first coupling transformer T1A first diode D1 is additionally connected between the synonym terminal of the secondary winding L2 and the first node N1, it being noted that the anode of the first diode D1, which has the reference ground GR, is connected to the first coupling transformer T1The synonym terminal and the cathode of the secondary winding L2 are connected to a first node N1. The source of excitation pulses PUS captured or induced by the secondary winding L2 from the mains is charged by the steering diode D2 to the storage capacitor C1 connected between the control terminal and the first terminal of the main switch M, i.e. to said storage capacitor C1 arranged between the gate G and the common node NCO, which steering diode allows the induced pulses to charge the storage capacitor unidirectionally. In an alternative embodiment, a parallel resistor R1 is further provided between the control terminal of the main switch M and the first terminal or common node NCO, in parallel with the energy storage capacitor. The induced excitation pulse source PUS charges the energy storage capacitor C1, the main switch M is turned on when the potential of the energy storage capacitor C1 reaches the turn-on threshold voltage of the main switch M, otherwise, the main switch M is turned off when the potential of the energy storage capacitor C1 does not reach the turn-on threshold voltage of the main switch M, and the reference ground GR may be a virtual ground.
With reference to fig. 4, the shutdown device SD essentially comprises a main switch M connected in series with the photovoltaic modules PV1-PVN via the power line and a first coupling transformer T1The first capacitor CC and the first diode D1 are omitted with respect to fig. 3. A first coupling transformer T is provided in the so-called shutdown device SD1Is connected in series with a main switch M having a first terminal and a second terminal and a control terminal. Wherein the first coupling transformer T1The secondary winding L2 is used to extract the excitation pulse source PUS applied to the power line, and as a coupling function of the signal, the excitation pulse source PUS signal induced or captured by the secondary winding L2 is charged via the steering diode D2 to the energy storage capacitor C1 connected between the control terminal of the main switch M, such as the gate G, and the first terminal, such as the source electrode S. In an alternative embodiment, a parallel resistor R1 is also provided between the control terminal of the main switch and the first terminal or common node NCO, in parallel with the energy storage capacitor C1. In thatIn an alternative embodiment, the steering diode D2 has its anode terminal directly connected to the dotted terminal of the secondary winding L2 and its cathode terminal connected to the control terminal of the main switch. A pair of anti-series connected zener diodes Z1-Z2 connected in parallel with an energy storage capacitor C1 is also provided between the control terminal of the main switch M and the first terminal or common node NCO. The reverse series connection of the zener diodes Z1-Z2 means: the anodes of zener diodes Z1 and Z2 are interconnected, the cathode of zener diode Z1 is connected to the first terminal or common node NCO, and the cathode of zener diode Z2 is connected to the control terminal of the main switch such that the pair of series connected zener diodes is connected in parallel with the energy storage capacitor C1, note that this embodiment may also be applied to the embodiment of fig. 3 as well. The back-to-back reverse series connected voltage stabilizing diodes are used for clamping the voltage drop between the control terminal and the first terminal of the main switch, and the power switch is prevented from being damaged. The first terminal of the main switch and the common node are in this embodiment directly coupled together with the same reference ground potential GR. In an alternative embodiment, a single zener diode, e.g., zener diode Z2 is retained and zener diode Z1 is eliminated, connected in parallel with the energy storage capacitor C1 between the control terminal of the main switch and the first terminal or common node NCO.
Referring to fig. 5, there are various ways in which the shutdown control module RSD supplies a periodic excitation pulse source PUS to the shutdown device SD or to the power line. In this embodiment: the excitation pulse source PUS is generated in the form of a high-low logic level by a pulse signal generator provided with the shutdown control module RSD. Second coupling transformer T2There is also a primary winding and a secondary winding and the secondary winding is connected in series on the power line, and the secondary winding and the shut-off device SD and also a series of photovoltaic modules PV1-PVN connected in series are connected in series via the power line. In addition, a second coupling transformer T is provided2The primary winding of which is connected in series with a coupling capacitor OC shown in the figure between a further reference ground GG, which is designated as the second reference ground potential, and the first reference ground potential, which is designated as the reference ground potential GR, can be different from each other. Then the switching-off control module RSD will produceThe generated excitation pulse source PUS is output via the provided driver DR, and the excitation pulse source PUS can be passed through the second coupling transformer T2The primary winding and the secondary winding of the transformer are coupled to be propagated or loaded onto the power line.
Referring to fig. 6, the shutdown control module RSD must continuously or intermittently send the excitation pulse source PUS when trying to control the shutdown device SD to be in the normal on state, and then the shutdown device SD senses the excitation pulse source PUS and charges its own energy storage capacitor to maintain the shutdown device SD on, that is, to satisfy the condition that the potential of the energy storage capacitor C1 reaches the on threshold voltage of the main switch. Accordingly, if the shutdown control module RSD no longer expects the shutdown device SD to be in a normal on state but to be turned off, for example, if the shutdown control module RSD receives a shutdown command in an emergency, the excitation pulse source PUS that is originally sent to the shutdown device SD continuously, intermittently or periodically may be stopped, in which case the energy storage capacitor C1 may be powered down and no longer meet the condition that the potential reaches the on threshold voltage of the main switch. The mode in which the shutdown control module issues a shutdown instruction to the shutdown device SD is: the supply of the periodic excitation pulse source to the shut-off device SD is stopped to inform the shut-off device SD to perform a shut-off operation on the battery string connected in series therewith. Introduction to the background section U.S. electrical specifications stipulate that the voltage of a photovoltaic power generation system must drop below 30 volts in 10 seconds, and the embodiment according to fig. 2-5 enables efficient and timely shutdown of the entire battery string, making the system safer and safer.
Referring to fig. 6, in an alternative embodiment of the shutdown control module RSD, as an alternative embodiment to the shutdown control module shown in fig. 5, the shutdown control module RSD includes a second coupling transformer T2And a first switch MP and further a second switch MD, which are both power semiconductor switches. A first switch MP and a second coupling transformer T are arranged2Is connected in series between a DC supply VCC and a reference ground GG, e.g. a second coupling transformer T2The same-name end of the primary winding is coupled to a direct current power supply VCC through a first switch MP, and a second coupling transformer T2Is coupled to said reference ground GG, a secondCoupling transformer T2Is connected in series with a series of photovoltaic modules and is also connected to a first coupling transformer T1Are connected in series. In an alternative embodiment, it is preferable to set the second coupling transformer T2Is coupled to the first coupling transformer T1And also sets the second coupling transformer T2Is correspondingly coupled to the first coupling transformer T1Even if a plurality of shutdown devices SD are connected in series in the series loop of the multi-stage photovoltaic module, the first coupling transformer T of any shutdown device SD can be set1The dotted terminal of the primary winding of the first coupling transformer T is correspondingly coupled to the dotted terminal of the secondary winding of the second coupling transformer, and the first coupling transformer T of the arbitrary shutdown device SD1The synonym terminal of the primary winding of the second coupling transformer is correspondingly coupled to the synonym terminal of the secondary winding of the second coupling transformer. In an alternative embodiment, the first and second switches are provided as complementary switches, meaning that one of them is on and the other is off at the same time. In an alternative embodiment, the on or off state of the set of complementary switches is substantially controlled by a driving signal or a control signal or a modulation signal output by a microprocessor MCU or the like, for example: logic devices, complex processors, control devices, state machines, controllers, chips, software-driven controls, gate arrays, and/or other equivalent controllers generate drive signals, where pulse width modulated signals are typical drive signals. In order to enhance the driving capability of the driving signal, the driving signal outputted from the microprocessor or the like is enhanced by the driver DR and then used to drive the first switch MP and the second switch MD. The second switch MP is connected in parallel with the primary winding of the second coupling transformer, e.g. the second switch MD is connected to the second coupling transformer T2Between the dotted terminal of the primary winding of (A) and a reference ground GG, or a second switch MD, is connected to a second coupling transformer T2And the interconnection node of both the primary winding and the first switch, and a reference ground GG. The driving signal drives the first switch MP to switch between on and off, the second switch MD is complementary with the first switch, and the direct current power VCC is applied when the first switch MP is switched onOn the primary winding of the second coupling transformer, when the first switch MP is turned off, the dc power VCC is immediately released from the primary winding of the second coupling transformer, so that the primary winding of the first switch MP is excited once in each switching period, and the square-wave pulse signal generated in the secondary winding by the excitation of the primary winding of the second coupling transformer is regarded as a pulse source. Whereby the primary winding of the second coupling transformer is intermittently excited by the DC power supply VCC and generates an excitation pulse source due to the second coupling transformer T2Is connected in series with a plurality of photovoltaic modules PV1-PVN via the power line, while a second coupling transformer T2Is used to couple the excitation pulse source PUS to the power line, such as to the bus bars LA-LB.
Referring to fig. 6, the method of attempting to restart the system again without hindrance after the shutdown device SD is shut down under the instruction of the shutdown command needs to be designed separately. Before the shutdown control module RSD waiting for the start command receives the start command, the shutdown control module RSD controls the shutdown device SD to enter the shutdown mode, so that the photovoltaic module corresponding to the shutdown device entering the shutdown mode cannot be connected between the dc buses to supply power to the dc buses. The main switch is opened, so that the bus can be opened to guarantee safety, but at the same time, the negative disadvantage is caused, namely that an excitation pulse source PUS sent by the turn-off control module RSD can not be smoothly propagated in a closed loop, wherein the closed loop refers to a loop formed by the main switch and a series of battery assemblies PV1-PVN connected in series and located between the buses LA-LB. The unique design of the system restart method is as follows: the shutdown device SD is further configured to perform an operation of recovering the battery string connected in series from the shutdown state to the re-series connection state, that is, when the shutdown control module RSD receives the start command, for example, a physical start switch/touch screen switch/voice control switch provided for triggering the shutdown control module RSD indicates that the start command is reached, the shutdown device SD is further configured to transmit a periodic excitation to the power lineThe pulse source PUS informs the shutdown device SD to perform the series reconnection operation on the battery string connected in series, which corresponds to the stage at which the shutdown control module RSD immediately sends the startup instruction again to the shutdown device. It has been discussed above that the opening of the main switch M causes the failure of the periodic excitation pulse source PUS, which is again fed to the cut-off device via the power line, to form a closed propagation path through the open main switch M, in other words, the failure of the secondary winding to sense a pulse, directly causes difficulties in the operation of the cut-off device SD to perform a series reconnection. The method for solving the problem that the excitation pulse source PUS is transmitted in the closed loop comprises the following steps: the turn-off device SD is further provided with a parallel capacitor CP connected between a first terminal, such as a source, and a second terminal, such as a drain, of the main switch M, and the parallel capacitor CP connected in parallel with the main switch M provides a conduction path for the excitation pulse source PUS to propagate on the power line after the turn-off device SD performs a turn-off operation and closes the main switch M. After the shutdown control module RSD receives the starting command, the shutdown control module instructs a shutdown device SD to recover the corresponding photovoltaic modules PV1-PVN from the shutdown state of the system shutdown stage to the serial connection state through an issued excitation pulse source PUS, the power generation system containing the photovoltaic modules PV1-PVN of the battery string is rapidly restarted, and the voltage of the direct current bus LA-LB is rapidly increased to be equal to VO1+VO2+…VON. The overall idea is that the parallel capacitor CP ensures that the excitation pulse source PUS can be transmitted when the main switch M is turned off, the main switch is turned on again by charging the energy storage capacitor with the aid of the excitation pulse source PUS, and the potential of the energy storage capacitor reaches the turn-on threshold voltage of the main switch, so that the turn-off device can perform the operation of series connection again on the battery string connected in series with the turn-off device. The embodiment of providing a parallel capacitance CP between the first and second terminals of the main switch in a normally-off or normally-on shut-off device may also be adopted in various other embodiments described hereinbefore and hereinafter, for example, in fig. 2-9.
Referring to fig. 7, in an alternative embodiment the turn-off control module RSD comprises a second coupling transformer T2And a first switch and a second switch MP/MD: setting a first switch MP and a second coupling transformer T2The primary winding of the transformer is connected in series with the DCA current source VCC and a reference ground GG, and a second switch MD connected in parallel with the primary winding. A first terminal, e.g. a homonymous terminal, of the primary winding is coupled via a first switch MP to a dc supply VCC and a second terminal, e.g. an alien terminal, of the primary winding is coupled via a first resistor RB, shown, to a reference ground GG. Optionally, an optional capacitor CB in parallel with the first resistor RB is also coupled between the second end of the primary winding and a reference ground GG. The second switch MD is coupled between a first end of the primary winding coupled to the first switch and a reference ground GG. The drive signal drives the first switch MP to switch between on and off and the second switch MD is complementary to the first switch. The DC power VCC is used to excite the primary winding during the on-phase of the first switch MP in each switching cycle, and the exciting current of the primary winding during the off-phase of the first switch MP in each switching cycle decreases to zero, i.e. the second coupling transformer is switched to the core reset state, whereby the second coupling transformer T is switched to the core reset state2Is intermittently excited by a DC power supply VCC and generates a source of excitation pulses due to a second coupling transformer T2The secondary winding of the transformer is connected with a plurality of photovoltaic modules in series through a power line, and a second coupling transformer T2For coupling the excitation pulse source PUS to the power line. Fig. 7 is a further development of fig. 6 in that a capacitor CB and a matching resistor RB are connected in parallel to the second coupling transformer T2And a reference ground GG.
Referring to fig. 8, the dc power supply can be used to energize the primary winding during the on-phase of the first switch MP in each switching cycle according to the above description. If the reference ground GG potential is considered to be the lowest reference potential among the shutdown control modules and when no remedial action is taken, the excitation pulse source PUS1 of the upper graph of fig. 8 has the disadvantage that: the exciting current of the primary winding in the off phase of the first switch MP is coupled to the second coupling transformer T in the process of reducing to zero2Has a portion below the reference potential, for example below zero potential, so that if the conduction phase of the second switch MD is assumed according to the TIME periods TIME1-TIME2 shown, the excitation pulse source PUS1 cannot charge the storage capacitor during this TIME, i.e. every TIME the excitation pulse source PUS1 of the secondary winding has a portion below the reference potential, for example below zero potentialThere is a power loss of the excitation signal for each switching cycle. This power loss, in addition to the natural signal attenuation of the excitation signal on each cell in the series-connected battery string, is inevitable, for example, when passing through the equivalent internal resistance of each cell, and perhaps the effective component of the excitation pulse source that can finally charge the energy storage capacitor is very weak, resulting in a malfunction of the main switch M, i.e., the enhancement transistor cannot be turned on or the depletion transistor cannot be turned off. In order to save the power loss of the excitation signal and avoid the transmission of the excitation signal to the turn-off device being too weak to cause the turn-off device to respond or delay the response, the first coupling transformer T is combined with the topology shown in fig. 7 and the combination of the first capacitor CC and the first diode D1 used in the embodiments of fig. 2-51When the secondary winding of the transformer is used for extracting the excitation pulse source PUS1 loaded on the power line, the excitation pulse source PUS2 induced across the secondary winding of the first coupling transformer in the TIME period TIME1-TIME2 is as shown in the lower diagram of fig. 8, and the topology is improved, which is equivalent to the disadvantage that the original excitation pulse source PUS1 cannot charge the energy storage capacitor in the TIME period TIME1-TIME2 in each period described above, so that each switching period has almost no excessive excitation signal power loss, and the scheme is also applicable to the embodiments of fig. 2-7 and fig. 9, that is, the topology of fig. 7 can play a role in remedying the power loss if the combination of the first capacitor CC and the first diode D1 is adopted in the embodiments of fig. 2-6 or fig. 9. If no improvement in the topology is attempted, the proportion of the on-time in the whole cycle must be increased in each switching cycle of the first switch MP, the range of the on-proportion is only 100% at the maximum, and it is assumed that in the extreme case 100% of the on-proportion cannot generate the required ripple signal, so that the power penalty of this solution is very limited. Another solution is to increase the frequency of the generated excitation signal corresponding to the switching frequency of the first switch MP, which is intended to save power and to remedy the power loss, while the switching frequency of the first switch MP is extremely increased at the source of the signal generation, and the first switch MP and the complementary switch MD consume excessive power directly at the source of the signal, which is the so-called switching loss, and the switching loss is usually too muchThe switching transistor is divided into three main parts of turn-on loss, turn-off loss and turn-on loss, and compared with a topology improvement mode, the extra power loss caused by increasing the switching frequency mainly comprises the two parts of the turn-on loss and the turn-off loss of the switching transistor.
Referring to fig. 9, in conjunction with the embodiments described in fig. 2-7, in the normally-off type turn-off device, when the potential of the energy storage capacitor reaches the turn-on threshold voltage of the main switch M, the main switch M is turned on, otherwise the main switch is turned off, the main switch M is an enhancement type power MOSFET by default, and the first, second and control terminals are the source, drain and gate, respectively, or the main switch is an IGBT by default, and the first, second and control terminals are the emitter, collector and gate, respectively. In Normally-OFF type turn-OFF devices, which means that the main switch M is Normally OFF, such as an NMOS transistor in enhancement mode, which is turned OFF only when the storage capacitor is charged until its potential exceeds the threshold voltage of the NMOS in enhancement mode, fig. 2-7 can basically employ a Normally-OFF (normal-OFF) switch such as a power MOSFET or an IGBT in enhancement mode. In the normally-off type turn-off device: when the turn-off control module RSD receives the turn-off command, the microprocessor configured to stop outputting the driving signal is equivalent to stopping transmitting the excitation pulse source to the turn-off device SD, that is, the energy storage capacitor has no charging source; in the normally-off type turn-off device: the turn-off control module RSD, when receiving the start command, configures the microprocessor to start outputting the driving signal, which is equivalent to transmitting the excitation pulse source to the turn-off device SD again through the power line to inform the turn-off device to perform the operation of re-connecting the series-connected battery strings, i.e. the energy storage capacitor has a charging source.
Referring to fig. 9, as an alternative to the embodiments described in fig. 2 to 7, in the turn-off device of the normal-on type, when the potential of the energy storage capacitor reaches the turn-off threshold voltage of the main switch M, the main switch is turned off, otherwise the main switch is turned on. In the normally-on type shutoff device: the main switch is a depletion mode JFET or a depletion mode power MOSFET and the first, second and control terminals are a source, a drain and a gate, respectively. For example, the main switch M is a depletion-mode P-channel JFET, so-called P-type JFET, which is a Normally-ON (normal-ON) switch, i.e., it is in an ON-state by default if it is not actively controlled to be in an ON or off state. The shutdown control module, upon receiving a shutdown command, starts to deliver a source of excitation pulses to the shutdown device SD to control the normally-on shutdown device to perform a shutdown operation on the battery string connected in series therewith: the storage capacitor C1 is charged at this time, and the potential between the gate and the source of the depletion type JFET is gradually increased to cause the gate and the source to be reverse biased until the P-type channel region is pinched off, so the turn-off threshold voltage in this embodiment includes the pinch-off voltage of the turn-off JFET, at which time the P-channel JFET is originally on but is turned off because the excitation pulse source charges the storage capacitor, and the drain D and the source S and the gate G are respectively labeled at three terminals of the P-channel JFET in fig. 9. In a normally-on turn-off device, when the potential of the energy storage capacitor reaches the turn-off threshold voltage of the main switch, the main switch is turned off, otherwise the main switch is turned on, it is also allowable that the main switch M is a depletion type P-channel metal oxide field effect transistor MOSFET, which is normally on by default but charges the energy storage capacitor C1 through the excitation pulse source, and the conducting doped channel region existing on the primary side between the source and the drain of the depletion type P-MOSFET is gradually turned off. In the normally-on type shutoff device: when the turn-off control module RSD receives the turn-off command, the microprocessor configured to the turn-off control module RSD starts generating the driving signal, which is equivalent to starting to transmit the excitation pulse source to the turn-off device SD, and starts to charge the energy storage capacitor C1, so that the potential of the energy storage capacitor C1 reaches the turn-off threshold voltage of the main switch M, and then the main switch is turned off. Or in a normally-on type shut-off device: when the turn-off control module RSD receives the start command, the microprocessor configured in the turn-off control module RSD stops outputting the driving signal DR, which is equivalent to stopping transmitting the excitation pulse source to the turn-off device through the power line, and the charge on the energy storage capacitor C1 is consumed by the parallel resistor or leaks rapidly, so that the potential of the energy storage capacitor falls below the turn-off threshold voltage of the main switch M and turns on the main switch M, thereby informing the turn-off device SD to perform the operation of re-series connection on the battery string connected in series with the main switch M. It should be noted that, for the depletion-type main switch, the off threshold voltage means that when the gate control terminal of the depletion-type main switch applies a voltage value exceeding the off threshold voltage, the depletion-type main switch enters a forced off state from a normal on state, and when the gate control terminal of the depletion-type main switch applies a voltage value lower than the off threshold voltage, the depletion-type main switch returns to the normal on state, so that the potential of the energy storage capacitor falls below the off threshold voltage of the main switch, and the depletion-type main switch is turned on.
Referring to fig. 9, as an alternative to the various embodiments described in fig. 2-7, the shutdown system for tandem photovoltaic modules is restarted after shutdown by, in a normally-on shutdown device: when receiving the start command, the turn-off control module RSD stops sending the excitation pulse source PUS to the turn-off device SD through the power line to prohibit charging of the energy storage capacitor C1, so that the potential of the energy storage capacitor falls below the turn-off threshold voltage of the main switch M and turns on the main switch M, for example, the potential of the energy storage capacitor falls below the pinch-off voltage of the depletion P-channel JFET to turn on the JFET, thereby triggering the turn-off device SD to perform an operation of returning from the turn-off state to the re-series connection state on the battery string connected in series therewith. The various embodiments described in fig. 2-7 are in contrast to the normally-off type of shut-off device: when receiving the start command, the turn-off control module RSD transmits again the excitation pulse source PUS to the turn-off device SD via the power line to start charging the energy storage capacitor C1, so that the potential of the energy storage capacitor reaches the turn-on threshold voltage of the main switch M and turns on the main switch M, for example, the potential of the energy storage capacitor reaches the threshold voltage of the enhancement N-MOSFET due to charging to turn on the NMOS transistor, and triggers the turn-off device SD to perform the operation of returning from the turn-off state to the re-series connection state on the battery string connected in series therewith.
Referring to fig. 9, the conduction channel region of the depletion mode P-channel junction field effect transistor is a P-doped type semiconductor material region and the control gate G is a highly doped N-doped type semiconductor material region, the source S provides hole conduction carriers and the drain D receives hole conduction carriers. When the gate-source voltage drop VGS is zero, an inversion layer channel exists in a channel region of the P-channel junction field effect transistor, current carriers can freely pass through, namely the battery pack string and the direct current bus are conducted to provide electric energy for a load, if the voltage drop of the energy storage capacitor is increased, the gate-source voltage drop is no longer zero but reaches the turn-off threshold voltage of the main switch, a PN junction between an N-type semiconductor region of the grid G and a P-type semiconductor region of the source S is reversely biased and is exhausted in a channel region of a source end, equivalently, the P-channel junction field effect transistor enters a turn-off region immediately after entering pinch-off, the main switch is turned off, and if the charge of the energy storage capacitor is released and is restored to zero gate-source voltage drop VGS again, the main switch is turned on again. The discharge of the charge on the energy storage capacitor requires, based on the reception of a start command by the shutdown control module RSD, the stopping of the delivery of the source of excitation pulses to the shutdown device SD through the power line to inform the shutdown device SD to perform the operation of re-series connection of the battery string connected in series therewith. Depletion type's junction field effect transistor JFET replaces the field effect MOS pipe of enhancement mode in this application and has had very big advantage, junction field effect transistor can not use parallel capacitance CP, excitation pulse charges energy storage capacitor when intention shutoff main switch M makes the main switch pinches off and cuts off, lead to the unable transmission of excitation pulse through the junction field effect transistor who turns off and cause junction field effect transistor to put through immediately again because energy storage capacitor's charge loss after pinches off and cuts off in step, mean at this moment that the excitation pulse source can propagate through the junction field effect transistor who switches on by oneself again, thereby make the cyclic from switch on to pinches off and switch on again and the adaptive entering hiccup mode of junction field effect transistor. The intermittent turning off of the main switch in the hiccup mode enables the component level turn-off capability to be satisfied and the intermittent turning on of the main switch enables the bus to have a bus voltage not higher than a predetermined voltage value, such as 30 v, which is necessary for the bus to have a predetermined voltage of a safe level, since the bus still needs to supply power to each power device, such as an inverter as an ac load or a dc power source VCC as a dc load. In the embodiment, the excitation pulse source does not continuously impact the single component, the photovoltaic component is impacted only when the main switch is supposed to be turned off, and even the main switch is turned off, the photovoltaic component is impacted only by the conducting time period in the hiccup mode, and the pinch-off time period and the cut-off time period in the hiccup mode do not strongly cause the pulse source to repeatedly impact the photovoltaic component, which is necessary for avoiding the change of the battery characteristics of the photovoltaic component, suppressing the aging of the battery and preventing the battery attenuation caused by the external pulse signal.
While the present invention has been described with reference to the preferred embodiments and illustrative embodiments, it is to be understood that the invention as described is not limited to the disclosed embodiments. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims of the present application should be considered to be within the intent and scope of the present invention.

Claims (13)

1. A shutdown system for a tandem photovoltaic module, comprising:
at least one shutdown control module and one or more shutdown devices;
a plurality of photovoltaic modules are connected in series to form a battery string and are also connected in series with a turn-off device;
the shutdown device is used for performing shutdown operation on the battery string connected with the shutdown device in series;
when receiving a turn-off command, the turn-off control module stops transmitting an excitation pulse source to the turn-off device to control the normally-off type turn-off device to perform turn-off operation on the battery pack string connected in series with the normally-off type turn-off device; or
When receiving a turn-off command, the turn-off control module starts to transmit an excitation pulse source to the turn-off device to control the normally-on turn-off device to perform turn-off operation on the battery pack string connected in series with the normally-on turn-off device;
the turn-off control module comprises a second coupling transformer and a first switch and a second switch:
setting a first switch and a primary winding of a second coupling transformer to be connected in series between a direct current power supply and a reference ground, and setting a second switch to be connected in parallel with the primary winding;
the driving signal drives the first switch to switch between on and off, and the second switch is complementary with the first switch, so that the primary winding of the second coupling transformer is intermittently excited by the direct-current power supply and generates an excitation pulse source; and
the secondary winding of the second coupling transformer is connected in series with the plurality of photovoltaic modules through a power line, and the secondary winding of the second coupling transformer is used for coupling the excitation pulse source to the power line.
2. A shutdown system for a tandem photovoltaic module as claimed in claim 1, wherein:
the turn-off device further comprises a main switch and a first coupling transformer, wherein the main switch and the first coupling transformer are connected with the photovoltaic modules in series through power lines;
a primary winding of the first coupling transformer is connected in series with a main switch provided with a first terminal, a second terminal and a control terminal;
the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on the power line;
the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode, and the potential of the energy storage capacitor is used for controlling the main switch to be switched off or switched on.
3. A shutdown system for a tandem photovoltaic module as claimed in claim 2, characterized in that:
in a normally-off turn-off device, when the potential of the energy storage capacitor reaches the turn-on threshold voltage of the main switch, the main switch is turned on, otherwise, the main switch is turned off; or
In the normally-on type turn-off device, when the potential of the energy storage capacitor reaches the turn-off threshold voltage of the main switch, the main switch is turned off, otherwise, the main switch is turned on.
4. A shutdown system for a tandem photovoltaic module as claimed in claim 3, wherein:
in the normally-off type turn-off device:
the main switch is an enhancement power MOSFET, and the first terminal, the second terminal and the control terminal are respectively a source electrode, a drain electrode and a grid electrode, or the IGBT is characterized in that the first terminal, the second terminal and the control terminal are respectively an emitter electrode, a collector electrode and a grid electrode; or
In the normally-on type shutoff device:
the main switch is a depletion mode JFET or a depletion mode power MOSFET and the first, second and control terminals are a source, a drain and a gate, respectively.
5. A shutdown system for a tandem photovoltaic module as claimed in claim 2, characterized in that:
a parallel resistor connected in parallel with the energy storage capacitor is arranged between the control terminal and the first terminal of the main switch.
6. A shutdown system for a tandem photovoltaic module as claimed in claim 2, characterized in that:
a voltage stabilizing diode connected with the energy storage capacitor in parallel is arranged between the control terminal and the first terminal of the main switch; or
A pair of voltage stabilizing diodes which are connected in series in the reverse direction and connected with the energy storage capacitor in parallel are arranged between the control terminal and the first terminal of the main switch.
7. A shutdown system for a tandem photovoltaic module as claimed in claim 2, characterized in that:
the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;
the dotted terminal of the secondary winding of the first coupling transformer is coupled to the control terminal of the main switch through the steering diode;
the dotted terminal is connected to the anode of the steering diode and the control terminal of the main switch is connected to the cathode of the steering diode.
8. A shutdown system for a tandem photovoltaic module as claimed in claim 2, characterized in that:
the synonym terminal of the secondary winding of the first coupling transformer is coupled to the first terminal of the main switch;
the dotted terminal of the secondary winding of the first coupling transformer is coupled to a first node through a first capacitor;
a first diode is connected between the synonym end of the secondary winding of the first coupling transformer and the first node;
the anode of the first diode is connected to the synonym terminal of the secondary winding of the first coupling transformer, and the cathode is connected to the first node;
the first node is coupled to the anode of the steering diode and the control terminal of the main switch is coupled to the cathode of the steering diode.
9. A shutdown system for a tandem photovoltaic module according to claim 2, characterized in that the shutdown device is further adapted to perform a recovery operation from a shutdown state to a re-series connection state for the string of cells connected in series therewith;
in the normally-off type turn-off device:
when receiving a starting command, the shutdown control module transmits an excitation pulse source to the shutdown device through the power line again to inform the shutdown device to execute the operation of re-series connection on the battery pack string connected with the shutdown device in series; or
In the normally-on type shutoff device:
the shutdown control module, upon receiving a start command, stops delivering the excitation pulse source to the shutdown device through the power line to inform the shutdown device to perform the re-series connection operation on the string of battery cells connected in series therewith.
10. A shutdown system for a tandem photovoltaic module as claimed in claim 9, wherein:
in the normally-off or normally-on type turn-off device, the turn-off device includes a parallel capacitance connected between a first terminal and a second terminal of the main switch;
the turn-off device thus performs a turn-off operation and, after the main switch is closed, a conduction path for the excitation pulse source to propagate on the power line is provided by a parallel capacitance connected in parallel with the main switch.
11. A shutdown system for a tandem photovoltaic module according to claim 1, wherein the primary winding of the second coupling transformer is coupled to the dc power supply via a first switch:
a first resistor is connected between the primary winding of the second coupling transformer and the reference ground; or
A first resistor and a capacitor connected in parallel with the first resistor are connected between the primary winding of the second coupling transformer and the reference ground.
12. A method for restarting a shutdown system for a tandem photovoltaic module after shutdown based on claim 1, wherein:
the turn-off device further comprises a main switch and a first coupling transformer, wherein the main switch and the first coupling transformer are connected with the photovoltaic modules in series through power lines;
a primary winding of the first coupling transformer is connected in series with a main switch provided with a first terminal, a second terminal and a control terminal;
the secondary winding of the first coupling transformer is used for extracting an excitation pulse source loaded on the power line;
the induced excitation pulse source charges an energy storage capacitor connected between the control terminal and the first terminal of the main switch through a steering diode, and the potential of the energy storage capacitor is used for controlling the main switch to be switched off or switched on;
the method comprises the following steps:
in the normally-off type turn-off device:
when the turn-off control module receives a starting command, the turn-off control module transmits an excitation pulse source to the turn-off device through the power line again to start charging the energy storage capacitor until the potential of the energy storage capacitor reaches the conduction threshold voltage of the main switch and turns on the main switch, and the turn-off device is triggered to perform the operation of recovering from the turn-off state to the re-series connection state on the battery pack string connected with the turn-off device in series; or
In the normally-on type shutoff device:
when the turn-off control module receives the starting command, the drive pulse source is stopped being transmitted to the turn-off device through the power line to prohibit the energy storage capacitor from being charged, the potential of the energy storage capacitor drops below the turn-off threshold voltage of the main switch and the main switch is switched on, and the turn-off device is triggered to carry out the operation of recovering from the turn-off state to the re-series connection state on the battery pack string connected with the main switch in series.
13. The method of claim 12, wherein:
in the normally-off or normally-on type turn-off device, the turn-off device includes a parallel capacitance connected between a first terminal and a second terminal of the main switch;
when the turn-off device performs turn-off operation and controls the main switch to be turned off, the parallel capacitor connected in parallel with the main switch provides a conduction path for transmitting the excitation pulse source on the power line.
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CN109818568A (en) * 2017-11-18 2019-05-28 丰郅(上海)新能源科技有限公司 Method for being restarted after the tandem turning off system of photovoltaic module and shutdown

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CN106602504A (en) * 2017-02-28 2017-04-26 阳光电源股份有限公司 Photovoltaic rapid turn-off device and photovoltaic system
CN109818568A (en) * 2017-11-18 2019-05-28 丰郅(上海)新能源科技有限公司 Method for being restarted after the tandem turning off system of photovoltaic module and shutdown

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